Field of the Invention
Embodiments of the present invention relate, in general, to footbeds, foot related orthotics, shoe and sandal technology and more particularly to methods and systems for establishing dynamic alignment of lower extremity musculature and skeletal components.
Relevant Background
Learning to walk is a complex skill. While most children learn to walk around 12 to 15 months of life, the learning process that makes those first steps possible begins months before. Around 4 months babies begin to control head and neck movement. Shortly thereafter they can roll from side to side by gaining control of their torso and by 6 months are able to roll completely over.
In a few months more, a child can sit upright and somewhere between 6-9 months babies begin to make attempts to crawl. With all of these skills mastered an infant can make the next major leap of standing and then walking. Within a few months of waddling, a mobile toddler soon becomes capable of a full out sprint.
This process is so natural that the complexity of walking or running is underappreciated. The human motion of walking is controlled by the neuro-muscular system. But bipedal walking and running requires not only an understanding of the neuro-muscular control system but an appreciation for several mechanical parameters (lengths, mass, distributions) as well.
From a simplistic point of view the bipedal motion of walking is akin to the motion of a pendulum. A pendulum is a device that transforms kinetic energy of motion into potential energy, and then back into kinetic energy. As the pendulum moves through the bottom of its arc the pendulum's velocity and thus its kinetic energy reaches a maximum. Thereafter that kinetic energy is converted back to potential energy as the pendulum comes to rest at its peak. With each step the human body becomes an inverted pendulum. But while a pendulum is incredibly efficient, the human body has some restrictions. One such restriction is when the arm of that pendulum, i.e. the leg, is not perfectly aligned.
An individual standing upright is a very stable structure. The triangle that is formed between the two legs, hip girdle and ultimately through the torso is a very stable geometric structure. The transverse extension of each foot with respect to the geometric plane formed by the two legs further stabilizes the structure. Indeed an individual standing still with their legs shoulder width apart represents a very stable and strong structure.
In such a configuration a knee that is perfectly aligned has its load-bearing axis on a line running down the middle of the leg, through the hip, knee and ankle. In a static configuration this line exists in what is referred to as the coronal or frontal plane. The coronal plane divides the body lengthwise, anterior from posterior, such that the face is separated from the back of the head, the chest from the back, the palms from the back of the hands, and the shins from the calves. But when walking, the body performs a pendulum motion about the sagittal plane. The sagittal plane bisects the left and right sides of the body longitudinally. This plane runs down the center of the head, torso and between the legs and feet.
As an individual walks or runs the neuro-muscular “control system” maintains a consistent center of gravity by shifting weight from one side of the sagittal plane to the other. In essence when you walk (or run) you lean and rest on one of your pendulums while repositioning the other. The problem lies in the fact that our pendulums are not so perfect.
Normally the outside part of the heel makes initial contact with the ground as an individual walks or runs. The foot rolls inward as it comes in complete contact with the ground where it can support the entire body weight. The rolling in of the foot optimally distributes the forces of impact. This movement is critical to proper shock absorption and a moderate amount of pronation, as defined herein, is required for the foot to function properly.
In a related condition called underpronation, as the outside of the heel makes initial contact with the ground the inward movement of the foot rolls less than for those with normal or flat feet. Consequently, forces of impact are concentrated on a smaller area of the foot (the outside part), and are not distributed as efficiently as with normally pronation.
Supination is the opposite of pronation and refers to the outward roll of the foot during normal bipedal motion. A natural amount of supination occurs during the push-off phase of running, and to a lesser extent during a walking gait as the heel lifts off the ground and the forefoot and toes are used to propel the body forward.
Pronation and supination, as they are classically understood, attempt to describe a complex three dimensional movement of the skeletal and neuromuscular structure of the foot. Other terms such as inversion vs. eversion, plantar flexion vs. dorsiflexion, and abduction vs. adduction describe various aspects of the complex task of bipedal motion. The dynamic interaction between the skeletal structure of the foot and its neuromuscular counterparts is very complex. For example, pronation is a skeletal collapse of the foot that is arrested by the surrounding musculature. Supination is thus the muscular over-reaction or over bias to the structural collapse. Moreover, while the musculature biases the foot toward supination the skeletal structure biases the foot to under-pronation. To efficiently and effectively achieve bipedal motion a balance between the cyclical activities of both pronation and supination must occur.
The interaction of the skeletal and neuro-muscular systems involved in walking and running is impeded when proper foot, ankle and knee alignment is not maintained. Unlike the very stable structure of an individual standing still with their legs spread, walking and running is inherently unstable and any misalignment of the mechanical components requires neuro-muscular compensation. The compensation requires energy and reduces overall endurance. Lastly, misalignment can ultimately result in injury and chronic pain.
There are many orthotic devices and supplemental footbeds designed to modify and correct misalignment of the knee, ankle and foot. Each, however, fails to consider the dynamic nature of bipedal motion. Moreover, misalignment issues vary from individual to individual and from one extremity to the other. Accordingly a preformed orthotic insert is not capable of addressing all of the varying corrective needs consistently or adequately. These and other deficiencies of the prior art are addressed by one or more embodiments of the present invention.